Dr. David Schoenfeld tells Anderson Cooper and Dr. Sanjay Gupta what it was like in the ER when the suspected Boston Marathon bombers were brought there last week. The doctor and the other staff had been treating victims of the attack and were on alert for more patients. Schoenfeld, who lives in Watertown, called his colleagues when he heard the gunfire and explosions early Friday.

"The folks in our department did a fantastic job preparing the emergency department for any number of trauma patients that were going to come in. So by the time I got there, the trauma bays were staffed and ready; the teams were divided up. We had additional staff coming in. The OR was, you know, ramping up. The whole hospital was ramping up," he said.

When suspect #1 arrived at Beth Israel Deaconess Medical Center with gunshot wounds and other injuries, Schoenfeld says their team did what they do with all trauma patients and tried to resuscitate him. He later died at the hospital.

Schoenfeld added that he's impressed by the first responders and civilians who rushed into the chaotic scene after the blasts to help the victims. He's grateful for their efforts, which helped save lives. "I'm proud to live in a city of heroes," he said.